Decomposing delta, theta, and alpha time–frequency ERP activity from a visual oddball task using PCA

Early diagnosis of dementia can be difficult. Quantitative EEG (qEEG) in combination with cognitive tasks shows promise for improving diagnostic accuracy. The study of task induced qEEG changes in normal ageing is a prerequisite for differentiating these changes from those which are specific to dementia. Sixteen young adults (mean age 28.8 ± 5.6 years) and 16 healthy cognitively normal older subjects (mean age 73.4 ± 7.9 years) participated in the study. EEG recordings were made while subjects were in a relaxed (or resting) state, and also while they performed arithmetic and language tasks. From the resting to the arithmetic conditions, there was decreased alpha activity and increased delta and beta-3 activity for both subject groups. Changes in alpha and delta activity were found in almost all sites and could be associated with arousal. Increase in beta-3 activity was focal, appearing only in the posterior region of the brain and it could be assumed that this area is highly involved in arithmetic processes. In the young adult group, theta activity increased from the resting to the arithmetic conditions, while in the older group theta activity changes were in the opposite direction. From the resting to the language condition, there was increased delta activity and decreased alpha and beta-1 activity for both subject groups. Changes in alpha and delta activity were again found in almost all sites. The decrease in beta-1 activity was found in only four sites, but these were not specific to a region of the brain known to be involved in language processing. This consistency in qEEG changes during cognitive tasks suggests that the method can be applied to the investigation of cognitive deficits associated with a number of neurological syndromes.

The aim of this study was to investigate topographic changes in electroencephalographic (EEG) power and frequency induced by abdominal surgery during anesthesia with 0.6% or 1.2% isoflurane in 66% nitrous oxide. Forty-six patients (aged 41 +/- 13 yr) scheduled for elective abdominal surgery were studied. The trachea of each patient was intubated and the lungs ventilated. Patients were randomly assigned to one of four groups: anesthesia was maintained with 0.6% (group 1, n = 12; group 2, n = 11) or 1.2% end-tidal isoflurane (group 3, n = 12; group 4, n = 11) in 66% nitrous oxide. Data were recorded over 20 min. Groups 1 and 3 were studied without surgery (as controls). In groups 2 and 4 recording was started 6 min before skin incision. The EEG was acquired via 17 scalp electrodes placed in standard International 10-20 locations (reference Cz). Absolute and relative power densities were calculated in selected frequency bands. EEG maps of spectral power densities were coded according to a continuous color spectrum. During baseline recordings, alpha activity was dominant at frontal areas in groups 1 and 2. In comparison, in groups 3 and 4, delta and theta activities were dominant at frontal leads. In group 2, the start of surgery resulted in increases in delta activity and decreases in alpha activity that were most dominant frontally (delta +181% and alpha -61%, F3). The delta shift was attenuated at 1.2% isoflurane (group 4, delta +44%, F3), but decreases in alpha activity (-53%, F3) were comparable to those in group 2. The EEG response in all frequency bands was attenuated at parietotemporal recording sites at both isoflurane concentrations. The current data demonstrate graded EEG responses induced by abdominal surgery during anesthesia with 0.6% or 1.2% isoflurane in 66% nitrous oxide. Spatial heterogeneities in absolute spectral power densities were reflected by color changes in the EEG maps. The topographic EEG analysis indicates that these changes were most dominant at frontal areas. The increases in delta and decreases in alpha activities may be related to intraoperative "paradoxical" electrophysiologic arousal phenomena.

EEG data obtained from 27 patients with presenile Alzheimer's disease (AD) and 28 patients with senile dementia of the Alzheimer type (SDAT) were compared with data from 30 age- and sex-matched controls. Both patient groups exhibited more pronounced delta and theta activity and less prominent alpha and beta activity than the controls. AD, however, was accompanied by more severe slowing than SDAT. The slowing was distributed in the left temporal and frontal regions in AD, and bilaterally in the frontal regions in SDAT. As the severity of the dementia increased, delta activity alone increased in AD, whereas, there were significantly greater increases in both delta and theta activity and decreases in alpha and beta activity in SDAT. These EEG differences appear to be related to the degree of brain damage and the speed of progression of the disease process.

Decomposition of biomedical signals for enhancement of their time–frequency distributions

Reversible Carbamazapine Encephalopathy With Frontal Intermittent Rhythmic Delta Activity

Prognostic value of the second ictal intracranial pattern for the outcome of epilepsy surgery

Amantadine infusions in mild dementia: acute double-blind placebo-controlled EEG mapping and psychometric studies

The author investigated the effects of epidurally administered buprenorphine (BPN) and clonidine (CLO) on the potentiation of halothane anesthesia in terms of the minimum alveolar concentration (MAC), hemodynamics, and electroencephalographic activity in the patients undergoing lower abdominal surgery. Thirty-four women (ASA-1) were studied after the epidural administration of either 10 ml saline (group A, n = 8), 10 ml saline with 0.4 mg BPN (group B, n = 13), or 10 ml saline with 150 micrograms CLO (group C, n = 13). The MAC of halothane was reduced by 32% in group B (p < 0.05), and by 23% in group C (p < 0.05) compared with group A. The delta activity on the electroencephalogram (EEG) was more dominant in groups B and C 20 and 30 minutes after the administration of BPN and CLO compared with group A. The alpha activity in group A was significantly greater than that in the other groups. The delta activity in groups B and C was increased significantly compared with group A. The blood pressure was significantly lower after the epidural administered of CLO in group C, compared with groups A and B. The study concluded that epidurally administered CLO significantly reduce the MAC of halothane and also resulted in significant acceleration of delta activity on the EEG, as did BPN. The mechanisms by which the central nervous system (CNS) is depressed by epidural BPN and CLO are different, but this may have resulted from their direct action on the CNS via the systemic and spinal absorption of BPN and CLO.

Background Stroke is a leading cause of death and disability worldwide. In addition cognitive impairment (and dementia) and depression are common sequelae. Additional assessment methods which would better inform early prognostication of these unfavourable outcomes would engender substantial clinical benefits. For example, more accurate prognostication would enhance clinical decisions regarding appropriate levels of rehabilitation or care. This thesis investigates the potential utility, in this context, of one such assessment methodology; quantitative EEG (QEEG), performed in the first days after stroke. Study 1 (Chapter 2) The primary aim was to investigate the relationship between post-stroke QEEG measures and cognitive outcomes. Resting-state EEG was recorded within 62–101h after onset of middle cerebral artery (MCA) territory, ischaemic stroke. QEEG indices sensitive to power of one or more frequency bands were computed. The functional independence measure and functional assessment measure (FIM–FAM) was administered at approximately 3-months post-stroke. Total (30 items) and cognition-specific (5 items) FIM–FAM scores were correlated with QEEG indices using Spearman's coefficient. Twenty cases (10 female; age range 38–84) were analysed. Two QEEG indices demonstrated highly-significant correlations with cognitive outcomes: relative alpha power across the scalp (ρ=0.67, p≤0.001) and frontal delta/alpha power ratio (ρ=−0.664, p≤0.001). These results demonstrate that QEEG measures are associated with cognitive outcomes, and may potentially inform prognostication of same. Study 2 (Chapter 3) The primary aim was to investigate the ability of QEEG indices to inform prognostication of cognitive outcomes, assessed using the Montreal Cognitive Assessment (MoCA). Resting-state EEG was recorded within 48-239h after stroke symptom onset. Various QEEG indices analysed across the scalp were calculated. The MoCA was administered at approximately 3-months post-stroke and scores correlated with QEEG indices using Spearman's coefficient. Binary logistic regression was employed, with cognitive impairment indicated by MoCA scores ≤25. Thirty-one participants (10 female, age range: 18-84) were included in the analyses. Two measures of alpha frequency slowing (relative power in the traditional upper theta frequency range in posterior regions and peak alpha frequency across frontal and posterior regions of the scalp) were significantly positively correlated with lower MoCA scores. Using regression analysis, relative power of slowed alpha activity from 2 posterior regions were selected as optimal predictors of cognitive impairment. The regression model utilising these QEEG measures was able to accurately prognosticate cognitive impairment outcomes in 81% of the participants (25/31). These results indicate that the power of slowed alpha activity, acquired within several days of stroke onset from several electrodes only, can inform early prognostication of post-stroke cognitive outcomes. This QEEG measure would be of clinical value given the substantial numbers of stroke patients whom are unable to complete cognitive assessments, such as the MoCA, prior to hospital discharge due to functional impairments (as was the case in 13% of the patients recruited in the study). Study 3 (Chapter 4) The aim of the final study was to investigate potential associations between pre-discharge QEEG indices and post-stroke depression (PSD) outcome measures as well as the ability of QEEG to inform prognostication of PSD. (Methodology is detailed in Study 2, above). Outcome was assessed using the Geriatric Depression Scale (GDS) at approximately 3-months post-stroke. GDS scores were correlated with QEEG indices using Spearman's coefficient. Binary logistic regression was used to build a QEEG model to classify depression, indicated by GDS scores ≤6 (out of 15). A significant correlation was obtained between PSD and an index of interhemispheric asymmetry of delta activity, patients with more symmetric delta activity tended to have higher GDS scores (r=-0.475, p=0.007, n=31). This variable was entered into the binary logistic regression model, however, it was not found to be a statistically significant predictor of subsequent PSD. Conclusions The results of the studies reported in Chapters 2 and 3 collectively indicate that QEEG markers sensitive to alpha activity – particularly alpha slowing – following ischaemic stroke can inform early prognoses regarding post-stroke cognitive impairment. Notably, pre-discharge measures of slowed alpha activity, from several electrodes only, was found to reliably predict cognitive outcomes in the majority of patients investigated. Importantly, virtually all patients can be assessed with EEG, including the substantial proportion of patients who cannot be assessed with more routine assessment scales such as the MoCA; hence QEEG would be of particular clinical value in such cases. It is postulated that the observed associations between post-stroke measures of alpha slowing and cognitive outcomes are reflective of attentional function which appears linked to both variables. These novel findings and interpretations constitute the principal contributions of this thesis to the knowledge base in this field. In summary this research has considerable potential to ultimately contribute towards enhanced care and benefits for stroke patients and the broader community.

Antibodies against human c-myc protein have been reported to inhibit DNA polymerase activity and endogenous DNA synthesis in isolated nuclei, suggesting a role for c-myc in DNA replication. Using the same antibody preparations, we observed equivalent inhibition of simian virus 40 DNA replication and DNA polymerase alpha and delta activities in vitro, as well as inhibition of DNA synthesis in isolated nuclei. However, the c-myc antibodies could be completely separated from the DNA synthesis inhibition activity. c-myc antibodies prepared in other laboratories also did not interfere with initiation of simian virus 40 DNA replication, DNA synthesis at replication forks, or DNA polymerase alpha or delta activity. Therefore, the previously reported inhibition of DNA synthesis by some antibody preparations resulted from the presence of an unidentified inhibitor of DNA polymerases alpha and delta and not from the action of c-myc antibodies.

We investigated the propagation properties of Lamb waves in a GIS tank, using time–frequency analysis to diagnose the insulation performance of GIS. We measured the acoustic signals excited by metallic particles colliding with the tank sheath, and those emitted by partial discharge in the GIS. The wavelet transform was used to decompose the wave data into its time–frequency components. As a result, it was confirmed that Lamb waves with the dispersive property of the velocity are excited and propagate in a spiral path along the tank wall due to the cylindrical structure of the tank. Taking these results into consideration, we propose a new technique for identification of defect locations in GIS based on time–frequency analysis of acoustic signals with the wavelet transform. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(3): 25–32, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10163

Cannabinoids, particularly Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), have gained popularity as alternative sleep aids; however, their effects on sleep architecture and next-day function remain poorly understood. Here, in a pilot trial, we examined the effects of a single oral dose containing 10 mg THC and 200 mg CBD (THC/CBD) on objective sleep outcomes and next-day alertness using 256-channel high-density EEG in 20 patients with DSM-5 diagnosed insomnia disorder (16 female; mean (SD) age, 46.1 (8.6) years). We showed that THC/CBD decreased total sleep time (-24.5 min, p = 0.05, d = -0.5) with no change in wake after sleep onset (+10.7 min, p > 0.05) compared to placebo. THC/CBD also significantly decreased time spent in REM sleep (-33.9 min, p < 0.001, d = -1.5) and increased latency to REM sleep (+65.6 min, p = 0.008, d = 0.7). High-density EEG analysis revealed regional decreases in gamma activity during N2 sleep, and in delta activity during N3 sleep, and a regional increase in beta and alpha activity during REM sleep. While there was no observed change in next-day objective alertness, a small but significant increase in self-reported sleepiness was noted with THC/CBD (+0.42 points, p = 0.02, d = 0.22). No changes in subjective sleep quality, cognitive performance, or simulated driving performance were observed. These findings suggest that a single dose of cannabinoids, particularly THC, may acutely influence sleep, primarily by suppressing REM sleep, without noticeable next-day impairment (≥ 9 h post-treatment). Australian New Zealand Clinical Trial Registry (ACTRN12619000714189) https://www.anzctr.org.au/.

To investigate other physiologic changes that occur with periodic leg movements during sleep (PLMS) that might be considered to be more sensitive indices of sleep fragmentation. Although PLMS are associated with recurrent microarousals (MA), the frequency of PLMS with MA does not correlate with objective daytime sleepiness. It is postulated that the lack of correlation results from the low sensitivity of the standard criteria used to score MA. Ten drug-free patients with a polygraphic and clinical diagnosis of restless legs syndrome (RLS) and PLMS were examined. The EEG correlates of PLMS were analyzed by visual scoring and spectral analysis during PLMS that ended in a visible microarousal (PLMS with MA) or not (PLMS without MA). The R-R interval in the EKG signal was also examined. A total of 34% of PLMS were associated with MA lasting >3 seconds, and 3% of PLMS were associated with MA lasting <3 seconds. Although PLMS with MA were associated with an increase in alpha activity, for PLMS without MA a significant increase in delta and theta activity was present. Both types of PLMS induced a shortening of the R-R interval; this was particularly more marked for PLMS with MA. First, visual scoring of MA that include a duration of less than 3 seconds has little effect on the detection of PLMS with MA. Second, EEG activation and tachycardia are present during both types of PLMS. Third, a hierarchy in the arousal response is present-going from autonomic activation to bursts of delta activity to alpha activity to a full awakening.

High resolution parametric description of slow wave sleep

Histamine and dopamine contribute to the maintenance of wakefulness. This study aims to conduct an exploratory analysis of the effects of 10 and 50mg of MK-0249, a novel histamine subtype-3 receptor inverse agonist, and 200mg of modafinil, a presumed dopaminergic compound, on EEG power spectra during sleep deprivation and subsequent recovery sleep. A total of 25 healthy men were recruited to a double-blind, placebo-controlled cross-over design. EEG power spectra, an electrophysiological marker of changes in sleepiness and vigilance, were obtained at the beginning of wake maintenance tests at two-hourly intervals throughout a night and day of sleep deprivation, which is an established model of excessive sleepiness. After placebo, sleep deprivation was associated with enhancements in delta and theta and reductions in alpha and beta activity. Following dosing at 02:00 h, MK-0249 and modafinil reduced delta and theta activity and enhanced alpha and beta activity, compared to placebo. During recovery sleep initiated at 21:00h, latency to sleep onset and number of awakenings were not different from placebo for any of the active treatments. Wake after sleep onset and stage 1% was increased and total sleep time, SWS% and REM% were reduced after both doses of MK-0249. Compared to placebo, MK-0249, the 50-mg dose in particular, reduced activity in some delta and theta/alpha frequencies and enhanced beta activity during NREM sleep and REM sleep. After modafinil, no changes were observed for power spectra during sleep. Both MK-0249 and modafinil exert effects on the EEG which are consistent with wake promotion.